This application claims the priority of German application 196 38 323.4, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to an improved method for operating an internal combustion engine the fuel is introduced into an intake port of the internal combustion engine and is heated in the region of the intake port at least during the cold-start phase of the engine before its entry into the cylinder. Furthermore, the present invention relates to an improved internal combustion engine having an intake port for feeding fuel to an injection valve of a cylinder, an injection nozzle which ejects the fuel, and a heat source which at least indirectly heats the fuel located in the intake port.
DE 40 24 005 A1 discloses an internal combustion engine having an intake port in which a heat source of plate-shaped configuration is arranged between an injection nozzle and an intake valve. The fuel coming from the injection nozzle strikes the heat source which is inclined transversely to the injection direction. As a result, the fuel is heated and vaporized. The heating of the fuel results in better preparation of the air-fuel mixture, thus reducing the pollutants in the exhaust gas during the cold-start phase. In the process, however, fuel condenses on the cold spots in the intake port, and thereby, in particular, in the region around the intake valve (the valve itself being included in the valve region and referred to throughout as the valve region for simplicity) as well as on the remaining walls of the intake port. This condensation has a negative effect on the pollutant emission.
U.S. Pat. No. 5,297,530 discloses a heating element mounted in a region between an intake valve and an injection nozzle. The fuel jet coming from the injection nozzle and injected into an intake port of a cylinder passes the heating element, just like parts of the inflowing fresh air, with consequent heating of the air-fuel mixture. Here, as well, the heating operation results in better preparation of the mixture, and as a result the pollutants in the cold-start phase are reduced. Despite the relatively high structural outlay for the heating element, however, fuel still condenses on the walls of the intake tract with this known configuration.
An object of the present invention is to improve the method for operating an internal combustion engine so that, in conjunction with a low structural outlay, the characteristics of internal combustion engines are improved in the cold-start phase, and thereby, particularly, the pollutant emission is improved.
Furthermore, it is another object of the present invention to prove a basic internal combustion engine for the aforementioned purpose.
These objects have been achieved in a method in which at least areas of the walls of the intake port are irradiated by an electromagnetic radiation and heated without contact in the region of an intake valve, and in which liquid fuel is at least partially vaporized in the valve region by contact with the valve region.
An improved basic internal combustion engine is achieved by providing a heat source which is a radiation source having electromagnetic radiation wavelength within the absorption spectrum of the fuel and/or of the material present in the region of the intake valve (termed valve region below for simplicity) and/or of the material of the walls of the intake port, and in that the radiation is aimed at least indirectly at at least the valve region.
Irradiating the air-fuel mixture and/or the inner wall of the intake port with a radiation source which is easy to introduce results, during cold starting, in favorable heating, the fuel located there. A particular advantage of the present invention results from the use of radiation to heat at least the walls in the valve region, because then no fuel, or only a slight amount of fuel, can condense in this region on the cold areas of the intake tract.
Preventing condensation of the fuel a particularly favorable recognition by way of injection nozzles which preheat the fuel and thereby, in particular, vaporize the fuel is also a particularly favorable contribution and recognition of the present invention. The at least slight condensation of fuel on the walls of the intake port results, for example, in reduction of the mixture enrichment of the air-fuel mixture in the cold-start phase. In the best case, fuel enrichment, which relates to the condensation effect, can be dispensed with entirely.